GCRIS

Now showing 1 - 2 of 2

Experimental and Numerical Evaluation of the Blast-Like Loading of Fiber Reinforced Polymer Composites and Aluminum Corrugated Core Composite Sandwiches Through Projectile Impact Testing Using Aluminum Corrugated Projectiles
(Izmir Institute of Technology, 2015) Odacı, İsmet Kutlay; Güden, Mustafa; Taşdemirci, Alper
This thesis develops and validates a laboratory scale blast-like testing method that can simulate explosive blast tests in air and under water without using explosives. The study has mainly focused on the shock loading potential of 1050 H14 trapezoidal corrugated core aluminium sandwich structures on E-glass/polyester composite plates and corrugated core composite sandwich structures experimentally, numerically and analytically. The composite plates were modelled using MAT_162 material model in LS-DYNA finite element code. Quasi-static and high strain rate tests were performed to determine the material model parameters of composite and corrugated structure. The resultant parameters were calibrated and validated by comparing the numerical results with the experimental results. The planar shock wave formation and propagation in corrugated core sandwich structures were shown experimentally using a direct impact Split Hopkinson Pressure Bar test set-up. Rigid-perfectly-plastic-locking material model and Hugoniot jump relations revealed the shock loading potential of the tested corrugated core sandwich structures. The shock loading response of composite plates and sandwich structures were investigated by firing the corrugated sandwich projectiles on the targets. These impact tests were also simulated numerically and an analytic model was used to predict the plate deflections. The experimentally, numerically and analytically determined back face deflections were compared with the deflections of the Conwep blast simulations in LS-DYNA. The results have shown that the corrugated core sandwich structures can generate shock loading as in the explosive blast tests and can be used to produce shock loads in laboratory scale experiments.
Experimental and Numerical Approaches To Evaluate the Crushing Behavior of Combined Geometry Core Sandwich Structures Against Blast
(Izmir Institute of Technology, 2015) Kara, Ali; Taşdemirci, Alper; Güden, Mustafa
In this study, novel sandwich structures containing combined geometry structures as core materials were designed and developed for blast protection applications. The proposed combined geometries consist of a hemispherical geometry attached seamlessly to a cylindrical segment. Deep drawing method was used to obtain four different types of combined geometries having two different radii from blanks with two different initial thicknesses. The mechanical properties of the blank material were obtained by conducting tensile experiments at quasi-static and high strain rate regimes. Thereafter, crushing and energy absorption behavior of core units were determined by tests at quasi-static and low velocity regimes, experimentally. Before crushing simulations, manufacturing method was simulated to have realistic residual stress/strain and thickness variations of numerical specimens. Having accurate deformation history, crushing experiments were simulated and a good agreement was reached proving the realistic modeling of the manufacturing effects. The effect of heat treatment on the crushing behavior of combined geometry shells was also investigated both experimentally and numerically and there was a good agreement noted. After, cross-shaped sandwich structures of one type of combined geometry were prepared. Static, low velocity and high velocity crushing behavior of sandwiches were investigated. Study on sandwich structures also included confined experiments in order to account for the interaction between the core units and between the core units and surrounding environment; such a case might be a bigger sandwich in which adjacent cores could exert forces to each other. Numerical study was validated by comparing experimental and numerical results of three different loading regimes for sandwiches. Having well-verified numerical models, numerical study was extended to investigate strain rate and inertial effects on sandwich structures by simulations at high crushing velocities. With complete knowledge on crushing and energy absorption of single geometries and sandwiches, behavior of sandwiches under blast was investigated by using ConWep function. Various types were proposed for arrangements of sandwiches to have higher energy absorption and lower transmitted forces to the protected structures.

Phd Degree / Doktora

Browse

Filters

Settings

Sort By

Results per page

Search Results